Adding image textures in texture paint
The way I do this is pretty useful to me, so I will share this method here:

First, select the images you want to use and make copies in a new folder, renaming them with whatever tool or program you want to follow a sequence like 'image.001, image.002, etc' so that the same image name is shared and they follow a sequential number.

Load them as a new brush texture or brush mask depending on what you want to use them as.



Add a timeline editor to your workspace if not present, and set the end frame number to match the number of images in your image sequence.


Use the playhead controls or the left/right arrow keys to switch images as you paint.


Another neat trick is that you can press the Play button and paint, your dabs will change texture corresponding to where the play head is on the timeline. This can be used for many effects like randomly mixing wear images or changing scratch marks, or even just imitating Alchemy for idea generation.